Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
  • G21C21/02—Manufacture of fuel elements or breeder elements contained in non-active casings
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/30—Nuclear fission reactors

Definitions

• MIMAS "Mlcron- ized MASter Blend” - see for example D. Haas, M. Lippens “MOX FUEL FABRICATION AND IN-REACTOR PERFORMANCE", Proc. of the Internat. Conference on Future Nuclear Systems, GLOBAL 97, p.489 a 494).
• MIMAS "Mlcron- ized MASter Blend” - see for example D. Haas, M. Lippens “MOX FUEL FABRICATION AND IN-REACTOR PERFORMANCE", Proc. of the Internat. Conference on Future Nuclear Systems, GLOBAL 97, p.489 a 494).
• This separate preparation of a powder free of plutonium reduces the volume of plutonium containing powder that has to be milled, and allows the production of fuel pellets of various plutonium contents with a unique plutonium treatment chain by changing only the rate of admixed uranium powder.
• the present invention aims to overcome these drawbacks and to propose a method as indicated above which leads to fuel pellets of the MOX type in which the distribution of plutonium throughout the pellet is substantially more homogeneous.
• the method according to the invention implies the separate preparation of a Pu-U oxide powder on the one hand and an uranium oxide powder free of plutonium on the other hand.
• the Pu-U oxide powder is prepared conventionally by mechanically milling Pu0 2 and U0 2 materials, whereas the U0 2 powder is prepared as follows: To an aqueous solution of uranyl nitrate small amounts, i.e. between 0.5 and 2 wt%, of organic thickeners are added, such as ethocel, dextran, polyvinyl alcohol, such that the viscosity of the solution is adjusted to values between 20 and 100 centipoise. There-after, this solution is dispersed into droplets, which are introduced into an ammonia bath. In this bath, due to the network formed by the long chain organic polymers, precipitation occurs within the original droplets, so that nearly spherical beads are formed.
• organic thickeners such as ethocel, dextran, polyvinyl alcohol
• these beads depends on the size of the droplets produced during dispersion. In a preferred embodiment these beads present diameters of between 20 and 50 ⁇ m. These beads are then washed to remove nitrate salts (ammonium nitrate salts in the above example) and organic polymers, and are subjected to an azeotropic distil- lation using an immiscible organic solvent such as C 2 C1 4 to remove water.
• nitrate salts ammonium nitrate salts in the above example
• organic polymers organic polymers
• the beads are in a hydroxide form, from which they are converted to oxide by a thermal treatment of between 2 and 6 hours duration and at about 400°C in air. Thereby residual organic polymers are pyrolysed.
• the beads are then again submitted to a thermal treatment of between 4 and 8 hours duration, this time at about 800°C and in a reducing atmosphere of Ar/5%H 2 , to convert U 3 0 8 to U0 2 .
• the beads can be produced by conventional uranium processing facilities (no ⁇ contamination). They are free flowing, dust free and do not require any further mechanical treatment such as milling prior to mixing with the powder containing plutonium.
• the homogeneity of the finally produced fuel can further be enhanced by sieving the beads and retaining only beads with diameters in the range of 20 to 50 ⁇ m. Alternatively this result can also be achieved by using a droplet dispersion device which produces droplets of well defined size such that the bead diameters remain within said range and no sieving becomes necessary.
• pellets are then sintered at high temperature, preferably at 1700°C, in a humidified Ar/H 2 atmosphere, the hydrogen content of which lies between 1 and 6% and the water vapour introduction should result in a ratio of the partial H 2 pressure to the water vapour partial pressure of between 20 and 60.
• the water allows to control the oxygen potential of the gas atmosphere which results in an enhanced diffusion and in a more homogeneous fuel thus enabling a longer burn-up in the reactor.
• the powder containing an excess content of plutonium can be prepared in the same way as above described for the uranium oxide powder, but by starting with uranyl-plutonium nitrate instead of uranyl nitrate.
• the inventive method can be realised in conventional MOX fabrication facilities and conserves all the advantages of the MIMAS process but does not suffer from the drawbacks of this process as mentioned above.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Manufacturing & Machinery (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)
• Catalysts (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
• Acyclic And Carbocyclic Compounds In Medicinal Compositions (AREA)

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• 1999
  • 1999-09-06 AT AT99116886T patent/ATE266892T1/de active
  • 1999-09-06 DK DK99116886T patent/DK1081716T3/da active
  • 1999-09-06 PT PT99116886T patent/PT1081716E/pt unknown
  • 1999-09-06 DE DE69917257T patent/DE69917257T2/de not_active Expired - Lifetime
  • 1999-09-06 ES ES99116886T patent/ES2219963T3/es not_active Expired - Lifetime
  • 1999-09-06 EP EP99116886A patent/EP1081716B1/en not_active Expired - Lifetime
• 2000
  • 2000-08-17 CA CA002382626A patent/CA2382626C/en not_active Expired - Fee Related
  • 2000-08-17 JP JP2001522550A patent/JP5153981B2/ja not_active Expired - Fee Related
  • 2000-08-17 US US10/031,407 patent/US6733699B1/en not_active Expired - Lifetime
  • 2000-08-17 WO PCT/EP2000/008057 patent/WO2001018822A1/en not_active Ceased
• 2002
  • 2002-03-05 NO NO20021088A patent/NO334069B1/no not_active IP Right Cessation

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